Non-invasively measured root diameters of maize (left) and barley (right) by MRI. Root lengths per diameter class were summed (n=4 and n=6 for maize and barley respectively) and compared with excavated and scanned roots (gray symbols, see middle pane) for maize (top) and barley (bottom).

Knowledge of how plant roots grow in their natural environment, soil, is vital to find plant genotypes that have improved yield or survival rates under stress. Technologies that can penetrate the soil, visualize the roots and especially allow to quantify root traits, like length, diameter and distribution, are very scarce. Here, we demonstrate that Magnetic Resonance Imaging (MRI) is such a technology when applied properly. This opens up new ways to non-invasively study plant root responses to realistic, relevant environmental factors, like limited water supply, reduced nutrition levels and pests.